Particulate or fibrous adsorbent materials which can adsorb a wide variety of liquid and vapor phase contaminates are often incorporated in textile materials for the production of protective clothing, various liquid or vapor filter media, or the like. Examples of adsorbent materials which have been used are activated carbon, natural and synthetic zeolites, ion exchange resins, silica gel, alumina and other synthetic carbonaceous materials.
Due to the particulate or fibrous nature of these materials, however, in most such applications the material must be attached in some fashion to a substrate material. As an example, U.S. Pat. No. 4,250,172 to Mutzenburg et al. discloses a sandwich-type material wherein a particulate adsorbent is held between at least two fibrous mats. The multi-layered product is held together by needling, which mechanically interlocks the fibers of the respective layers in the thickness direction.
In another example, U.S. Pat. No. 4,411,948 to Ogino et al. describes an air-cleaning filter element prepared by adhesively adhering an adsorbent material, such as activated carbon, evenly across the opposed surfaces of a pair of three-dimensional mesh-structured elastic-flexible webs. Once the adsorbent is adhered to each of the webs, the opposed faces thereof are adhesively joined together to form the overall filter element.
The above described products, however, are undesirable in several respects. First, because the fibrous structure of the products is interrupted through the thickness of the product by the contained adsorbent material, the integrity in the thickness direction is weakened, leading to delamination and spillage of the adsorbent material. Second and from a manufacturing standpoint, the process for producing these products must include a needling, adhesive or other step to laminate the overall product. These additional steps are both costly and cumbersome. Third, with respect to those products where an adhesive is used to join the various layers, the adhesive tends to coat the active surfaces of the adsorbent material and thereby to unfavorably impact its adsorptive properties. And lastly, due to their multi-layered nature, such products are generally thicker and bulkier than desired, especially when the material is intended for use in protective clothing.
A third type of product similar to the present invention is disclosed in U.S. Pat. Nos. 4,397,907 to Rossen et al., and 4,540,625 to Sherwood, both assigned to Hughes Aircraft Company. These patents disclose an in situ composite containing organic polymeric fibers and solid adsorbent particles or fibers. The composites are prepared by providing a hot polymer solution of a fiber-forming polymer material and subsequently adding thereto a desired solid adsorbent material to form a suspension. The temperature of the solution is lowered while the solution is agitated whereby the polymer crystallizes to form fibers which precipitate from the solution, taking with them the solid adsorbent material. The resultant composite, which may be deposited onto a woven substrate to provide added structural integrity, may be used in protective clothing or as a filter medium or the like.
Although this product overcomes some of the above listed disadvantages, this product, for obvious reasons, must be made via a batch process, which is both costly and unsuited for mass production.
It is therefore an object of this invention to provide a strong, unitary textile product having excellent adsorptive qualities, that can be mass produced with relative ease, has structural integrity through its thickness, and can be produced at thicknesses easily incorporated into the protective clothing and small-sized liquid or vapor filters.